The replication of JHM virus, a murine coronavirus, will be studied. The physical organization of virion RNA and intracellular virus specific m-RNAs will be studied by oligonucleotide fingerprinting. Virus-specific m-RNA will be translated in vitro and the proteins they code for identified by gel electrophoresis, radioimmune precipitation and tryptic maps. The transcription of virus specific RNA will be studied by the UV inactivation and by the "Northern blot" technique. The persistence of murine hepatitis virus in cell culture will be studied. Persistently infected cell cultures will be examined for the presence of defective interfering particles and interferon. Alterations in the biochemical properties of virus released from persistently infected cultures will be examined by 2-dimensional gel electrophoresis and tryptic peptide mapping. Alterations in the biologic properties and neuropathology induced by these viruses will be studied.